The invention relates to abrasive flap discs which are used for a variety of finishing, grinding and polishing operations, particularly on welded fabrications.
Generally, flap discs comprise a relatively stiff backing plate onto which abrasive flaps are adhered. The backing plate can be angled, flat, depressed, raised, or a combination of these variations. They are typically 4xe2x80x3-9xe2x80x3 (10.16 cm-22.86 cm) in diameter, although smaller diameter discs are being introduced. The abrasives used are ordinarily 24-120 grit.
There are alternatives to flap discs, such as Depressed Centre (resin bonded) Grinding Wheels (DCGWs). However, these are only suitable for removing large amounts of material and generally can not provide suitable finishing. Thus, the use of Sanding Discs (SDs) is required subsequent to the grinding operation. Unlike these two aforementioned counterparts, flap discs are multi-purpose, this being partly attributable to the fact that the surface operation performed by them is somewhat dependent upon the pressure applied by the operator.
Furthermore, the superior properties of flap discs over DCGWs are attributable to the fact that flap discs use coated abrasives (unlike bonded abrasives for a DCGW), which inherently present the majority of the abrasive grit particles at their optimum cutting attitude whilst providing a potentially xe2x80x9csofterxe2x80x9d operation, removing material at a variable rate dependent upon the pressure applied and contributing to an improved surface finish. Flap discs are also considered superior to SDs due to the use of multi-layer coated abrasives, which provide a substantially greater amount of useable abrasive cloth, in the region of 20:1, to provide a substantially longer life for the flap discs.
Although flap discs are xe2x80x9csofterxe2x80x9d than DCGWs, flap discs are still xe2x80x9chardxe2x80x9d, particularly when finer grit sizes are used, and as such do not lend themselves to contouring or blending work. There have been moves to develop flap discs which are xe2x80x9csofterxe2x80x9d, but these have concentrated on providing a backing plate with reduced stiffness, e.g. Zircotex (RTM). In such cases, this has not been wholly successful as the necessary combination of a xe2x80x9cflexiblexe2x80x9d disc and xe2x80x9csupport padxe2x80x9d have proved to be too rigid. Thus, the operational range of these flap discs are significantly limited. Moreover, the configuration of flap discs prevents them from being capable of dressing sharp corners.
The present invention provides an abrasive flap disc comprising a backing plate, an annular array of flaps of abrasive material arranged on the backing plate and bonded thereto along the lowermost edge of each flap, wherein each flap, at least in a radially outer region, is substantially spaced from each adjacent flap such that the flaps have freedom to flex and conform to an underlying surface in use.
Preferably, each flap does not contact an adjacent flap at all. Alternatively, each flap contacts an adjacent flap along its radially inner edge.
Preferably, the angle between the backing plate and each flap is in the range of approximately 20xc2x0 to approximately 90xc2x0. Advantageously, the angle between the backing plate and each flap is in the range of approximately 40xc2x0 to approximately 70xc2x0.
In one embodiment, the abrasive flaps of the disc may be arranged such that a centerline of each flap, which extends between its radially inner and outer edges, is substantially on a radius of the backing plate.
Alternatively, the centerline of each flap may be at an angle to a radius of the backing plate. Advantageously, the angle between each flap centerline and a radius of the backing plate is in the range of approximately between 5xc2x0 to approximately 85xc2x0. Most preferably, the angle between each flap centerline and a radius of the backing plate is in the range of approximately between 30xc2x0 to approximately 60xc2x0.
Preferably, the flaps comprise abrasive grit bonded to a backing material and the backing plate includes means to attach the disc to a drive mechanism.
The invention further provides a method of producing an abrasive flap disc of the type described above, comprising the steps of providing a backing plate, providing an adhesive on an upper surface of the backing plate; rotating the backing plate incrementally; at each incremental step, feeding the end of a strip of abrasive material on to the adhesive on the backing plate; severing the end of the strip to form a flap repeating the process until an annular array of flaps is formed on the backing plate with each flap, at least in a radially outer region, being spaced from each adjacent flap, maintaining the flaps in the spaced position; and curing the adhesive to secure the flaps to the backing plate.
Preferably, after constructing the array of flaps and before curing, the method further includes the step of placing the disc in a former adapted to prevent each flap falling into substantial contact with an adjacent flap.
The former may include a cylindrical wall dimensioned to encircle the disc and prevent each flap falling into substantial contact with an adjacent flap. Alternatively, a spoke-shaped frame may be placed with a spoke positioned between adjacent flaps, to prevent each flap falling into substantial contact with an adjacent flap.
In one embodiment, the strip of abrasive material is fed such that each flap has a centerline extending from its radially inner to outer edge which is substantially on a centerline of the backing plate.
Alternatively, the strip of abrasive material may be fed such that each flap has a centerline extending from its radially inner to outer edge which is at an angle to a radius of the backing plate.
The invention therefore provides flap discs having an arrangement of abrasive flaps which give the flaps pliability and increased-freedom to flex and conform to an underlying surface, thereby increasing the applicability of flap discs whilst maintaining sufficient support for the abrasive flaps such that the operational range of the abrasive flap discs is also maintained. Specifically, the flap disc operator can use a single tool to perform a number of functions, efficiently controlling the operation performed by the pressure and angle of approach applied to the tool. Moreover, the arrangement of abrasive flaps provided is still sufficiently stiff such that the grinding of particularly rough surfaces is possible. In particular, the flap discs of this invention can be used in contour and blending work, and also to dress sharp corners.
It is recognised that there are other processes for the manufacture of flap discs which differ in specific ways from the normal process referred to above. However the invention is valid regardless of how the cloth and flaps are presented, cut or adhered to the backing plate.